Monitoring and modeling of water and related nutrient fluxes in rice-based cropping systems

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Many studies have been conducted with the aim to better understand biologic and hydrologic processes that control C and N fluxes in rice paddy systems. But rarely have studies attempted to explicitly link the hydrological and biogeochemical controls of nutrient transport on the field scale. In this research project we aim to improve our understanding of processes that are involved in storing and releasing water and nutrients of different rice-based cropping systems. The Catchment Modeling Framework (CMF) will be coupled to the biogeochemical MOBILE-DNDC model (SP6) in to simulate (1) vertical and lateral transport processes of water, C and N and (2) to predict the reaction of ecosystem services such as water storage and purification, gas regulation, nutrient cycling and food supply in dependence of cropping systems. SP7 follows a rejectionist framework where model complexity is adapted to available data and process understanding. State-of-the-art analytical instruments will be connected to a unique automatic sampling system to continuously measure water isotopic composition as well as dissolved carbon and nitrogen solutes in situ for the first time. Waters to be sampled include surface water, irrigation water, groundwater and water vapor. Cavity Ringdown Spectroscopy will be used to measure 2H/H and 18O/16O. Isotopic signatures will allow estimating water mean transit times, partitioning between evaporation and transpiration and separating flow paths. Hyperspectral UV photometers equipped with a flow-through cell will be installed for continuous measurements of nitrate and DOC.